1. Field of the Invention
This invention relates to a wafer processing apparatus including a wafer mapping apparatus having a function of detecting the presence or absence of a wafer. Also, this invention particularly relates to a wafer processing apparatus for detecting the presence or absence of a wafer on each shelf of a rack (shelves) on which the wafer is placed and which is provided in the interior of a clean box for keeping a wafer in a good condition for use in a semiconductor product, a product related to an electronic part, an optical disc product or the like during the manufacture thereof.
2. Related Background Art
In recent years, in a wafer processing process in the manufacture of a semiconductor product or the like which requires a high degree of cleanness, there has been adopted a technique which does not an entire room relating to the treating process into a highly clean environment. In this technique, a small space (hereinafter referred to as minienvironment) kept highly clean is provided in each wafer processing apparatus in a wafer manufacturing process. This aims at keeping a small space only in the wafer processing apparatuses and a container (hereinafter referred to as the pod) for keeping the wafer in a good condition during the movement among those wafer processing apparatuses at a high degree of cleanness. Thereby, facility investment and facility maintenance expenses required when the entire room relating to the wafer treating process is kept in a highly clean environment are curtailed to thereby obtain the same effect as keeping the entire room relating to the wafer processing process in a highly clean environment and realize an efficient production process.
In the pod, there are disposed a rack having shelves on each of which a wafer is placed. In these shelves, wafers are contained in such a state that a shelf is allotted to a wafer. The wafers placed on the shelves are moved in each wafer processing apparatus with the movement of the pod. In some cases, however, there occurs a wafer which does not satisfy a predetermined standard in the processing process of each wafer processing apparatus, and the wafer which does not satisfy the predetermined standard is removed from the shelf in the pod. Accordingly, at the initial stage of the manufacture, each shelf of the rack (shelves) is filled with the wafer, but as each processing step of the wafer processing apparatus progresses, the number of shelves in the pod on which the wafer is absent increases.
The wafer processing apparatus automatically effects the treatment of the wafer and therefore usually it is provided with a wafer transport robot (hereinafter simply referred to as the transport robot). The transport robot gains access to a shelf of the rack in the pod, transports the wafer and executes the wafer processing process. Although a wafer to be processed is absent on that shelf, if the transport robot gains access to that shelf on which the wafer is absent in order to transport the wafer, there will occur a useless movement process from after the transport robot gains access to that shelf until it returns to its original position. Further, as such a useless movement process increases, the amount of processed wafers is reduced as a whole. So, it becomes necessary to detect the presence or absence of the wafer on each shelf of the rack in the pod in each wafer processing apparatus to thereby judge in which shelf of the shelves in the pod in each wafer processing apparatus a wafer is contained and in which shelf a wafer is not contained (mapping).
The detection of the presence or absence of the wafer for mapping will now be described with reference to FIG. 1 and FIGS. 7A and 7B to 9 of the accompanying drawings. FIG. 1 shows the whole of wafer processing apparatus 50. The wafer processing apparatus chiefly includes a load port portion 51 and a minienvironment portion 52. The load port portion 51 and the minienvironment 52 are partitioned by a partition 55 and a cover 58. A stand 53 is disposed on the load port portion 51. A pod 2 can be placed on and fixed to the stand 53. The stand 53 is movable on the load port portion 51 toward or away from the minienvironment 52 side. The interior of the minienvironment 52 is kept at a high degree of cleanness to process a wafer 1. The robot arm 54 of a transport robot for effecting the transport of the wafer 1 is provided in the minienvironment 52. The pod 2 has an opening portion in one surface thereof, and includes a box-shaped main body portion 2a having a cavity space for containing the wafer 1 therein, and a lid 4 for sealing the opening portion. A shelf having a plurality of shelves is disposed in the main body portion 2a. The wafer 1 can be placed on each of the plurality of shelves. Each of the shelves is disposed with a predetermined spacing from the shelf adjacent thereto so that adjacent wafers 1 may not contact with each other.
An access opening 10 is formed in the minienvironment 52 on the load port portion 51 side. The position at which the access opening 10 in the minienvironment 52 is disposed is a position at which the pod 2 fixed onto the stand 53 is right opposed to the opening portion of the pod 2 when it is moved on the load port portion 51 toward the minienvironment 52 side so as to become proximate to the access opening 10.
FIGS. 7A and 7B are enlarged views of an opener 3 in a conventional wafer processing apparatus. The opener 3 is provided near the access opening 10 inside the minienvironment 52. The opener 3 includes a door 6 and a door arm 42 of an elongated shape. A bar extending perpendicularly to the lengthwise direction of the door arm 42 is disposed at one end of the door arm 42. On the other hand, a fixing member 46 having a through-hole is attached to the door 6, and the bar provided at one end of the door arm 42 extends through this hole in the door 6, whereby the door 6 is pivotably fixed to the door arm 42. The other end of the door arm 42 is formed with a hole. The door arm 42 is rotatably supported by this hole being coupled to a hole at the tip end of a rod 37 which is a portion of an air-driven type cylinder 31 by a pivot 40. A through-hole is formed between the aforementioned one end and the other end of the door arm 42, and a pin extends through this hole and a hole in a fixing member 39 fixed to the support member 60 of a movable portion 56 to thereby constitute a fulcrum 41. Accordingly, the door arm 42 is pivotable about the fulcrum 41 by the expansion and contraction of the rod 37 by the driving of the cylinder 31. The fulcrum 41 of the door arm 42 is fixed to the support member 60 provided on an upwardly and downwardly movable portion 56. The door 6 has holding ports 11a and 11b, and can hold the lid 4 of the pod 2 by vacuum absorption. The opener 3 is mounted on the movable portion 56 vertically movable to move up and down the door arm 42 and the door 6 together with each other. The movable portion 56 is vertically movable along the wall surface of the minienvironment 52.
Accordingly, when the processing of the wafer is to be effected, the pod 2 is first disposed on the stand 53 so as to approach the access opening 10, and the lid 4 is held by the door 6. When the rod of the cylinder 31 is then contracted, the door arm 42 is moved about the fulcrum 41 so as to move away from the access opening 10. By this movement, the door 6 is pivotally moved with the lid 4, and the lid 4 is detached from the pod 2. Thereafter, the movable portion 56 is moved downwardly and the lid 4 is transported to a predetermined retracted position.
In the detection of the wafers 1 on the shelves of the rack in the pod 2, it becomes necessary for a detector to scan each shelf at least once while sweeping along a direction in which the wafers 1 are stacked, to thereby effect the detection of the wafers 1. To effect this sweeping movement for detecting the wafers 1, various methods are conceivable. For example, there is a method of providing a detector on a portion of the robot arm 54 and moving the detector by this robot arm 54 to thereby execute the detecting operation. The robot arm 54, however, is a device originally prepared to effect the transport of the wafer 1, and if the robot arm 54 is to effect the detection of the wafer, the robot arm 54 cannot perform the transporting operation for the wafers 1 during the detecting operation, and this leads to the disadvantage that the amount of treated wafers 1 is reduced.
As another method, there is a method of providing a detector on a portion of an opening and closing device for the lid 4 of the pod 2 and detecting the wafer 1 by the detector during the unsealing of the lid 4. FIGS. 7A and 7B show an apparatus adopting this method. In this apparatus, there is provided a mapping frame 5 comprised of a frame member disposed so as to surround the door 6. A pair of bar-like members 13a and 13b are disposed on the upper portion of the mapping frame 5. A transmitting type sensor 9 as a detector is mounted on the tip end of each of these bar-like members 13a and 13b. The transmitting type sensor 9 forms a pair by an emitter 9a and a detector 9b. FIG. 8 is a view of the mapping frame 5 of this apparatus as it is seen from its upper side. As shown in this figure, these bar-like members 13a and 13b have their respective one end fixed for the pivotal movement about shafts 36a and 36b on the mapping frame 5, and are rotated by cylinders 34a and 34b disposed also on the mapping frame 5 and can evolve so as to protrude from the mapping frame 5 toward the interior of the pod 2. That is, when the detecting operation for the wafer 1 is not executed, the bar-like members 13a and 13b are contained so as to be within the width of the mapping frame 5 along the axis of the frame of the mapping frame 5 (a bar-like member 13c and a bar-like member 13d). When the detection of the wafer 1 is to be effected, the bar-like member 13c and the bar-like member 13d are rotated by nearly 90 degrees about shafts 36a and 36b, respectively, by a cylinder 34a and a cylinder 34b and the bar-like members 13a and 13b evolve toward the wafer 1. In this state, the emitter 9a attached to the tip end of the bar-like member 13a and the detector 9b attached to the tip end of the bar-like member 13b become opposed to each other. When the bar-like members 13a and 13b evolve so as to protrude from the mapping frame 5, slots are formed between the emitter 9a and the detector 9b. The emitter 9a and the detector 9b are mounted so that the edge portion of the wafer 1 may be located between these slots. Also, the mapping frame 5 is mounted on the movable portion 56 so as to be moved up and down with the door 6. Further, the mapping frame 5 is supported also by the rod of another cylinder 43 so as to be movable up and down discretely from the door 6.
Reference is now had to FIG. 9 to describe the mapping of a wafer processing apparatus having the wafer mapping function. To carry out mapping in this apparatus, the pod 2 is disposed on the stand 53 so as to be proximate to the access opening 10, and the lid 4 is held by the door 6. When the rod of the cylinder 31 is contracted, the door arm 42 is moved about the fulcrum 41 so as to separate from the access opening 10. Then the door 6 is pivotally moved with the lid 4 and the lid 4 is detached from the pod 2. Here, when the emitter 9a and the detector 9b have evolved, the rod of the cylinder 32 is contracted to a preparatory position in which it becomes insertable into the interior of the pod 2 (a position located from the edge of the opening in the pod 2 to the vertically lower side which is the inner side of the pod 2) to thereby move down the mapping frame 5. After the mapping frame 5 has been moved down to the preparatory position, the cylinder 34a and the cylinder 34b are actuated to thereby evolved the emitter 9a and the detector 9b. Thereupon, the emitter 9a and the detector 9b become inserted into the interior of the pod 2. In this state, as shown in FIG. 8, when the wafer 1 is seen from a direction perpendicular to the surface of the wafer 1, there is brought about such a positional relation that the wafer 1 exists in the slot between the emitter 9a and the detector 9b. When here, the movable portion 56 is moved down, the mapping frame 5 is moved down with the door 6, and the slot between the emitter and the detector crosses the end portion of the wafer 1 to be located when the wafer 1 exists on each of the shelves. The emitter 9a and the detector 9b can scan each shelf of the shelves which sweeping along the direction in which the wafers 1 are stacked, to thereby detect the presence or absence of the wafers 1 and effect mapping.
The above-described method, however, has suffered from the following problems.
(1) The emitter 9a and the detector 9b disposed on the mapping frame 5, in order to prevent them from interfering with the pod 2, are designed to be capable of evolving so as to be rotated by the cylinders 34a and 34b and protrude from the mapping frame 5 toward the interior of the pod 2. The evolving mechanism, including such an air cylinder, is generally liable to produce dust. Further, in this structure, it is necessary that the cylinder 34a and the cylinder 34b be disposed in proximity to the pod 2. This leads to the problem that the dust produced from the cylinder 34a and the cylinder 34b adheres to the wafer 1 and causes the contamination of the wafer 1.
(2) Also, an air-driven type cylinder is used in the operation of opening and closing the door 6, the operation of moving up and down the door 6 and the operation of moving up and down the mapping frame 5. This is for obtaining a force necessary to appropriately crush a seal provided on the lid 4 of the pod 2 to keep the degree of cleanness in the pod. If a driving device for opening and closing the lid is a motor, a great load corresponding to a moment comprising the distance from the fulcrum 41 to the door 6 multiplied by a force necessary to appropriately crush this seal becomes necessary, and this leads to a disadvantageous problem. Accordingly, a driving device for pivotally moving the door 6 and a driving device for retracting the door 6 to a predetermined position are made discrete from each other, and both of them are air-driven type cylinders. In the mapping operation, however, the air-driven type cylinder poses the problem that there cannot be generated a reference signal indicative of the distance over which the emitter 9a and the detector 9b are actually moved, for contrasting with a signal generated when the slot between the emitter 9a and the detector 9b crosses the wafer 1, cannot be generated.
(3) Also, in the opening and closing apparatus of the type as previously described which is provided with a linear motor and in which the opener 3 is opened in a horizontal direction with the door 6, there is the problem that the production of dust from the linear motor cannot be prevented.